Polymer coated metals are well known. Their desirability stems largely from the combination of the advantages of a core metal substrate with those of an outer organic polymer coating. In the automobile industry, for example, the characteristics of a metal, such as aluminum, of resilience and conformability are often desirable for trim Pieces. Polymer coatings, while permitting the member to retain these desirable characteristics may augment resistance to the elements, including extreme temperature fluctuations, act as a sealant interface between the glass and an adjacent member such as a supporting frame, Provide a buffer between the metal and the glass of the windshield and Provide exposed Portions which are visually appealing.
The terpolymer of ethylene propylene diene monomer (EPDM), a thermosetting polymer, provides advantageous weathering and sealant characteristics. Polyvinyl chloride (PVC), a thermoplastic polymer, provides a smoother finish than EPDM, is available in a wider range of colors and tends to be more colorfast than EPDM.
An approach taken, in the automobile industry, to obtain a member with the characteristics of these materials has been to manufacture two metal strips, one partially coated with EPDM and the other partially coated with PVC. The strips are then assembled with the EPDM coating a portion of the assembly so as to act as a visually unexposed sealant and the PVC coating a Portion so as to be partly visually exposed on the assembled automobile.
A second approach has been to manufacture a member having a single strip of metal coated with a single Polymer such as EPDM, such a member lacking the advantage of a Portion coated with a second Polymer, such as PVC.
A third approach has been to extrude one of the polymers of EPDM or PVC onto suitably treated metal and then to attach the other of EPDM or PVC to the first extruded Polymer using an appropriate adhesive, such as an alkylcyanoacrylate compound or a hot melt adhesive, or mechanical attachment.
Generally speaking, the process of providing a metal strip with a PVC coating begins with rollforming the metal to the desired shape. The metal is then cleaned and dried. The cleaned metal is then coated with a heat activable adhesive. The coated metal is then heated to evaporate solvents from the adhesive and to activate the adhesive. The PVC is then extruded onto the metal, the activated adhesive serving to chemically bond the Polymer to the metal. Adhesives which require activation by heat, or exposure to utraviolet radiation, for example, are herein referred to as activable adhesives.
Generally speaking, the process of providing a metal strip with an EPDM coating begins with rollforming the metal to the desired shape. The metal is then cleaned, dried and coated with Primer. Solvents of the primer are evaporated and the coated metal is baked to fasten the primer thereto. A heat-activable adhesive is applied in similar fashion to the primer. The adhesive is activated by heat prior to extrusion of EPDM onto the metal. After extrusion, the EPDM on the metal is suitably cured. A one-coat adhesive system may be used instead of the two-coat system described above and has been used successfully in the past by Co-Ex-Tec Industries of Concord, Ontario, Canada.